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<p>Climate change significantly threatens agricultural water security, especially in semi-arid regions with high cropping intensity and limited water resources. This study assesses current and future irrigation water requirements in the Hemavathy command area of Karnataka, India, using the CROPWAT 8.0 model integrated with historical meteorological data from the Indian Meteorological Department (1985–2014) and projected climate data from the MIROC5 regional climate model under RCP 4.5 and RCP 8.5 scenarios (2020–2035). Spatial interpolation of climatic variables was performed using the Thiessen polygon method to generate area-weighted averages across the command area. Gross Irrigation Requirement (GIR) was estimated based on seasonal cropping patterns and effective rainfall using the Soil Conservation Service (SCA) method. Beyond standard irrigation demand estimation, the study introduces a Water Stress Index (WSI) to quantify the balance between irrigation demand and water availability, performs sensitivity analysis of key drivers (ET<sub>0</sub>, rainfall, crop coefficient), and evaluates adaptation scenarios including improved irrigation efficiency and crop pattern diversification. Results indicate a significant increase in irrigation demand under future climate scenarios, with projected requirements reaching up to 31.80 Thousand-Million m³ (TMC) under RCP 4.5, as compared to 27.13 TMC in 2012–2013 under historical conditions, accompanied by higher WSI indicating elevated irrigation stress. Sensitivity analysis highlights reference evapotranspiration (ET<sub>0</sub>) and rainfall as dominant controls on irrigation stress. Sensitivity analysis highlights ET<sub>0</sub> and rainfall as dominant controls on irrigation requirements, while adaptation scenarios demonstrate that integrated strategies can reduce irrigation demand by over 30% and lower WSI below the critical threshold. Analysis of reservoir inflow and groundwater yield revealed approximately 6.4 stressed years over 32 years, with groundwater alone insufficient to meet irrigation demand in most years. The study highlights the urgent need for integrated and adaptive irrigation strategies, including conjunctive water use, improved efficiency, and climate-responsive planning, to ensure agricultural sustainability under changing climatic conditions.</p>

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Evaluating irrigation water demand response to climate change scenarios with the CROPWAT model in the Hemavathy command area, Karnataka

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月24日

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  • D. V. Thirumalesha,
  • Radha Krishan,
  • Deepak Khare,
  • Prabhash Kumar Mishra

摘要

Climate change significantly threatens agricultural water security, especially in semi-arid regions with high cropping intensity and limited water resources. This study assesses current and future irrigation water requirements in the Hemavathy command area of Karnataka, India, using the CROPWAT 8.0 model integrated with historical meteorological data from the Indian Meteorological Department (1985–2014) and projected climate data from the MIROC5 regional climate model under RCP 4.5 and RCP 8.5 scenarios (2020–2035). Spatial interpolation of climatic variables was performed using the Thiessen polygon method to generate area-weighted averages across the command area. Gross Irrigation Requirement (GIR) was estimated based on seasonal cropping patterns and effective rainfall using the Soil Conservation Service (SCA) method. Beyond standard irrigation demand estimation, the study introduces a Water Stress Index (WSI) to quantify the balance between irrigation demand and water availability, performs sensitivity analysis of key drivers (ET0, rainfall, crop coefficient), and evaluates adaptation scenarios including improved irrigation efficiency and crop pattern diversification. Results indicate a significant increase in irrigation demand under future climate scenarios, with projected requirements reaching up to 31.80 Thousand-Million m³ (TMC) under RCP 4.5, as compared to 27.13 TMC in 2012–2013 under historical conditions, accompanied by higher WSI indicating elevated irrigation stress. Sensitivity analysis highlights reference evapotranspiration (ET0) and rainfall as dominant controls on irrigation stress. Sensitivity analysis highlights ET0 and rainfall as dominant controls on irrigation requirements, while adaptation scenarios demonstrate that integrated strategies can reduce irrigation demand by over 30% and lower WSI below the critical threshold. Analysis of reservoir inflow and groundwater yield revealed approximately 6.4 stressed years over 32 years, with groundwater alone insufficient to meet irrigation demand in most years. The study highlights the urgent need for integrated and adaptive irrigation strategies, including conjunctive water use, improved efficiency, and climate-responsive planning, to ensure agricultural sustainability under changing climatic conditions.